In a semiconductor device represented as an LSI, a bypass capacitor is provided in many cases as a noise suppression measure. The bypass capacitor is a capacitor to be interposed between a power supply line (Vcc line) and a ground (GND) in order to prevent a direct-current power supply voltage from changing when the semiconductor device operates. Providing the bypass capacitor makes it possible to reduce an alternating impedance of the power supply line to the ground and to filter a noise component so that it is not carried to a succeeding electronic circuit.
[Patent Document 1] Japanese Laid-open Patent Publication No. 5-21808
[Patent Document 2] Japanese Laid-open Patent Publication No. 2000-150789
[Patent Document 3] Japanese Laid-open Patent Publication No. 2002-16230
With a recent request for further miniaturization of a semiconductor device, miniaturization of a bypass capacitor, namely reduction in occupied area of the bypass capacitor is also requested. In order to obtain a desired capacitance with a small occupied area in a bypass capacitor, it is necessary to increase its capacitance density.
In the case when a bypass capacitor is provided in a semiconductor device, in order to reduce the number of manufacturing processes, it is preferable to use manufacturing processes of a functional element and the like of the semiconductor device and to form the bypass capacitor in the same processes with components of the functional element. For example, in a nonvolatile semiconductor memory such as a flash memory, in which stored information is not lost even if power is cut off, it is thought to use a stacked-type storage element having a capacitor insulating film sandwiched by upper and lower gates to thereby form a stacked-type bypass capacitor having the capacitor insulating film sandwiched by upper and lower electrodes. However, the capacitor insulating film of the storage element easily captures charge due to its property, and is inferior to dielectric breakdown resistance as the capacitor insulating film of the bypass capacitor, and causes a concern in terms of reliability, so that it is unsuitable.